Vectors of subsurface stormflow in a layered hillslope during runoff initiation

Abstract

Abstract. The focus is the experimental assessment of insitu flow vectors in a hillslope soil. We selected a 100 m 2 trenched hillslope study site. During prescribed sprinkling an obliquely installed TDR wave-guide provides for the velocity of the wetting front in its direction. A triplet of wave-guides mounted along the sides of an hypothetical tetrahedron, with its peak pointing down, produces a three-dimensional vector of the wetting front. The method is based on the passing of wetting fronts. We analysed 34 vectors along the hillslope at distributed locations and at soil depths from 11 cm (representing top soil) to 40 cm (close to bedrock interface).The mean values resulted as follows v x =16.1 mm min −1 , v y =−0.2 mm min −1 , and v z =11.9 mm min −1 . The velocity vectors of the wetting fronts were generally gravity dominated and downslope orientated. Downslope direction (xaxis) dominated close to bedrock, whereas no preference between vertical and downslope direction was found in vectors close to the surface. The velocities along the contours (yaxis) varied widely. The Kruskal-Wallis tests indicated that the different upslope sprinkling areas had no influence on the orientation of the vectors. Vectors of volume flux density were also calculated for each triplet. The lateral velocities of the vector approach are compared with subsurface stromflow collected at the downhill end of the slope. Velocities were 25-140 times slower than lateral saturated tracer movements on top of the bedrock. Beside other points, we conclude that this method is restricted to non-complex substrate (skeleton or portion of big stones).

Temporal variability of subsurface stormflow formation

“…Locations of the devices varied slightly on the different experimental slopes. At Lutertal, soil moisture content was monitored more closely with 30 additional TDR probes (Retter et al, 2006). Details on the experimental setup and uncertainties of the methods can be found in Kienzler and Naef (2008).…”

Quantifying spatial and temporal discharge dynamics of an event in a first order stream, using distributed temperature sensing

“…To observe the spatial and temporal distribution of lateral inflows, several researchers excavated trenches (Woods and Rowe, 1996;Weiler et al, 1998;Uchida et al, 2005;Retter et al, 2006;Gomi et al, 2008;Tromp-van Meerveld et al, 2008). Although these were able to give spatial and temporal flow information, installation of trenches is destructive and limited in size (2-60 m).…”

Pedological criteria for estimating the importance of subsurface lateral flow in E horizons in South African soils

“…In a vast range of catchments subsurface lateral flow (SLF) is considered a dominant streamflow generation process (Lorentz, 2001;Retter et al, 2006), not only during the recession limb of flow events, but also for peak and low flows (Harr, 1977;Mosley, 1979;Whipkey and Kirkby, 1979). SLF occurs either through the soil matrix (inter-granular pores or small structural voids) or through larger voids (macropores or pipes) (Atkinson, 1979).…”

“…Once conditions close to saturation are attained above the impeding layer, and there is a sufficient hydraulic head upslope from the profile in question, SLF will be generated. (Whipkey, 1965;Whipkey et al, 1979;Jackson, 1992;Woods and Rowe, 1996;Jackson, 2005;Kim et al, 2005;Retter et al, 2006). The relative importance of SLF can therefore be expressed mathematically:…”